1. Field of the Invention
The present invention relates to a platinum complex and an organic electroluminescent element (hereinafter, occasionally referred to also as “element” for short).
2. Description of Related Art
In the development of an organic electroluminescent element of recent years, studies on the improvement of external quantum efficiency have been conducted. Among such elements, an element containing a phosphorescence-emitting material comprising heavy metals such as iridium and platinum has attained high efficiency and attracted attention.
In the development of a luminescent material using platinum, an example in which an aryl group is linked by an ether linkage is described (for example, in Journal of Organometallic Chemistry, Vol. 689, pp. 2888 to 2899 (2004)). Such platinum complex is characterized by realizing a shorter luminescent wavelength than that of a quadridentate platinum complex such as an octaethylporphine platinum complex which has been reported (for example, in U.S. Pat. Nos. 6,303,238 B1 and 6,653,654 B1).
However, there is a problem in that the luminescence of the platinum complex described in Journal of Organometallic Chemistry, Vol. 689, pp. 2888 to 2899 (2004) is very weak at room temperature. Further, when a luminescent material contains remaining unidentate ligands, (particularly when a halogen atom such as a chlorine atom is used), the element using the luminescent material has low durability and improvements thereof have been needed.